1. Field
This invention pertains to compound archery bows, and specifically to mechanisms for dampening string vibrations following the launch of an arrow.
2. State of the Art
Casting an arrow with an archery bow involves first nocking the arrow to a bowstring and then pulling the bowstring at the nock point from its rest (brace) position to a drawn position. The limbs of the bow are thereby flexed to store energy. The string is released to cast the arrow, and returns to its rest (or brace) position. The energy stored in the limbs is transferred primarily to the arrow, but in part to the string. This string energy is dissipated through vibrations. Such vibrations are regarded as undesirable for several reasons. A peculiar sensation is experienced by the archer as vibrations transfer through the grip of the bow to the archer's hand and forearm. Moreover, the vibrations create noise, much as the vibrating string of a musical instrument. In a hunting environment, silence is considered to be essential. String vibration also contributes to a foreshortened useful life for the bowstring, due to fatigue. String vibrations, and their attendant disadvantages are particularly evident in compound bows.
Compound bows are available in many configurations, most of which are classified as either “single cam” or “dual cam” bows. U.S. Pat. Nos. 3,486,495; 3,990,425; 4,748,962; 4,774,927; 4,967,721; 6,763,818 and 6,990,970, the disclosures of which are incorporated by reference, describe a variety of constructions of such bows, including both single cam and dual cam configurations of cross bows. These bows are characterized by riggings (sometimes called “cable means”) that include a central stretch (bowstring) and multiple end stretches (cables) interconnecting opposed limb tips. The term “rigging” is intended to include such structure as pulley assemblies, bowstring, and cable(s) that are operable to flex the limbs of a bow as the bowstring is drawn. Most single cam bows and many dual cam bows include riggings that connect a pulley assembly carried by one limb to the opposite limb through a yoke (sometimes called a “Y” harness.) Such arrangements are characterized by riggings that include a bow string extending from a pulley member and a yoke harness extending from an axle member supporting that pulley member. The spacing between the string and harness changes as the string is moved between brace and drawn conditions. That spacing increases as the sting is drawn, and decreases as the string returns to brace condition following the launch of an arrow.
Various devices have been proposed to deaden or dampen string vibrations. For example, U.S. Pat. Nos. 4,061,125; 4,461,267; and 5,720,269 disclose various forms of string bumpers supported by the bow handle in position to contact the bow string in brace condition following launch of an arrow. U.S. Pat. No. 6,966,314 discloses a similar bumper arrangement (called a “suppressor”) that includes a support adapted for rigid attachment to the end of a bow limb. The distal portion of the support is configured to hold vibration suppressing material, such an elastomer or gel, against the string in rest, or brace, position. Such a suppressor may be connected to one or both limbs of the bow. The device disclosed by the '314 patent applies force received from the bowstring to only one side of the bow limb (to a single limb of a split limb bow, or an equivalent location on other limbs). This arrangement inherently imparts a twisting moment applied to the limb tip when the bow string encounters the damping element.